Project 1 has contributed to two paradigm changing discoveries. First, the androgen receptor (AR) pathway appears critical to the growth of castration-recurrent prostate cancer (CaP) in spite of castrate levels of circulating testicular androgens. Second, castration-recurrent CaP produces high tissue levels of testosterone (T) and dihydrotestosterone (DHT), the preferred AR ligand. Intracrine-produced testicular androgens present a target for novel therapies. Further advances may result from applying novel treatments to CaP coincidental with androgen deprivation therapy (ADT) when CaP cell death is at a maximum and surviving cells are under greatest stress. The central hypothesis of the proposed studies is that CaP can be cured or remission extended by a coordinated attack upon intracrine androgen metabolism and AR coincidental with elimination of circulating testicular androgens (medical or surgical castration). In order to test this hypothesis and allow the formulation of an appropriate clinical trial in advanced CaP, the response to ADT will be assessed using preclinical models in the immediate post-castration period. In general, cell or tissue sampling will be conducted just prior to castration and 12h and 1, 2, 4, 8, 16 and 30d after